Mechanisms of protection induced by attenuated simian immunodeficiency virus. IV. Protection against challenge with virus grown in autologous simian cells

Attenuated simian immunodeficiency virus (SIV) induces potent protection against infection with wild-type virus, but the mechanism of this immunity remains obscure. Allogeneic antibodies, which arise within animals as a result of SIV infection, might protect against challenge with exogenous SIV grown in allogeneic cells. To test this hypothesis, eight macaques were infected with attenuated SIV and subsequently challenged with wild-type SIV grown in autologous cells or heterologous cells. The results clearly demonstrated that animals infected with attenuated SIV are protected against wild-type SIV grown in autologous or heterologous cells. Thus, the hypothesis that live attenuated SIV protects by the induction of allogeneic antibodies is not tenable.

Cancer risk assessment

Increasing efforts to reduce the burden of cancer have brought into sharp relief the relevance of cancer risk assessment in preventing the occurrence and, when that is not possible, preventing the progression of the disease. Methods for estimating human cancer risk have evolved steadily over the past few decades as more has been learned about molecular, genetic, and biological aspects of cancer. These methods have been applied with increasing frequency in community-based approaches to reduce the risk of environmentally provoked cancers. At the same time, patients are showing increased interest in estimates of their likelihood of developing cancer during the next 10, 20, or 30 years. This interest is involving more physicians in human cancer risk assessment in clinical counseling settings.

IL-4 and TNF-alpha-mediated proliferation of the human megakaryocytic line M-O7E is regulated by induced autocrine production of GM-CSF

In this study, the authors examined the effects of recombinant human interleukin 4 (rhIL-4) and recombinant human tumour necrosis factor alpha (rhTNF-alpha) alone or in combination on proliferation of the human cytokine dependent myeloid cell line, M-O7e. While rhIL-4 or rhTNF-alpha alone induced only a weak proliferative response, a synergistic proliferative signal was clearly evident on stimulation of cells with a combination of both cytokines. The stimulatory effect of rhTNF-alpha is mediated predominantly by the 55-kDa TNF receptor because the agonistic monoclonal antibody htr-9 and the Trp32 Thr86 TNF-alpha mutant protein specific for this receptor type produced similar results to rhTNF-alpha. In contrast, the Asn143 Arg145 TNF-alpha mutant protein specific for the 75-kDa TNF receptor produced only minimal proliferation of M-O7e cells. Using RT-PCR, we found that rhTNF-alpha rapidly and strongly induced granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA production, while rhIL-4 was a slow and less efficient inducer of GM-CSF mRNA. However, there was little evidence of the TNF-alpha/IL-4 combination acting synergistically on GM-CSF mRNA production as the levels of GM-CSF mRNA increased only marginally compared with IL-4 or TNF-alpha alone. Thus, the observed synergistic effect of TNF-alpha/IL-4 costimulation of M-O7e cells seems to be mediated via induction of GM-CSF secretion rather than an enhanced production of GM-CSF mRNA. Higher levels of GM-CSF were detectable in supernatants of cells treated with both rhIL-4 and rhTNF-alpha than in cells stimulated with either cytokine alone. Furthermore, addition of a neutralising antibody against GM-CSF abrogated the observed synergistic effect of rhIL-4 and rhTNF-alpha treatment, indicating that the rhIL-4/TNF-alpha combination acts to significantly increase GM-CSF release which then acts in an autocrine manner to enhance the proliferation of M-O7e cells.

Distal vessel atherosclerosis as a cause for false-positive renal scintigraphy

While captopril-enhanced renal scintigraphy is acknowledged to be a useful screening technique to detect clinically silent obstructive lesions of the main renal arteries, the presence of significant atherosclerosis of distal, smaller renal vessels as a cause of positive scintigraphy scans has not been reported extensively. In a retrospective 2-year analysis of 31 consecutive captopril-enhanced renal scintigrams, we found a total of 13 studies in 11 patients that were classified as "positive" for renal artery stenosis. Of these 11 patients with positive scintigraphic studies, 4 patients underwent 5 renal arteriography procedures; only 1 of these renal arteriograms showed significant stenosis of the main renal artery. In the other 4 cases, an angiographic pattern of diffuse intrarenal distal arterial disease correlated with scintigram lateralization. Angiography was also performed in 4 patients with negative captopril renal scintiscans. In each of these cases the arteriogram was also negative for significant renal artery stenosis, and only 1 patient had diffuse bilateral intrarenal arterial disease. We conclude that distal renal arterial narrowing should be considered in the differential diagnosis of lateralized renal scintigrams. A negative renal scintigraphic study may be more reliable for excluding significant main renal artery obstructive disease.

Murine epidermal growth factor peptide (33-42) binds to a YIGSR-specific laminin receptor on both tumor and endothelial cells

A laminin-antagonist peptide, comprising amino acids 33-42 of murine epidermal growth factor (mEGF-(33-42)), interacts with a breast cancer- and endothelial cell-associated receptor, which is specific for the laminin B1 chain sequence, CDPGYIGSR-NH2 (Lam.B1-(925-933)), and is immunologically similar to a previously described 67-kDa laminin receptor. In whole cell receptor assays, mEGF-(33-42), Lam. B1-(925-933), and laminin all have IC50 values for displacement of 125I-laminin in the range 1-5 nM. Cell attachment to solid-phase laminin is also blocked by all three ligands, but in contrast to the receptor assays, mEGF-(33-42) or Lam.B1-(925-933), while equipotent with each other, were less effective than laminin. The concentrations of the peptides required to produce half-maximal inhibition of attachment were in the range 230-390 nM, but those for laminin were 1000-fold lower, in the range 0.2-0.3 nM. Like laminin, solid-phase mEGF-(33-42) supports cell attachment, and this ability is blocked by anti-67-kDa receptor antibodies. Modeling studies suggest that both peptides present a tyrosyl and an arginyl residue on the same face of a right-handed helical fold with elliptical cross-section.

MMPI-2 patterns in African-American females

Researchers have reported conflicting conclusions about the relation of the MMPI (MMPI-2) clinical scale elevations and race. Consequently, this study examined the concurrent validity of the MMPI-2 in evaluating African-American females. Seventy-eight (78) African American college student volunteers were administered the MMPI-2, along with other measures of personality, achievement, and coping style. Scores revealed 76% of the sample had elevated profiles. Subjects were divided into three groups based on frequency of clinical scale code type. Subjects with the 5/9 profile elevations functioned as well as normals on measures of coping skills and mood disorders. Discussion emphasizes the importance of clinical interpretation of MMPI data in research programs and the relationship of the data to coping style.

Molecular architecture of a toxin pore: a 15-residue sequence lines the transmembrane channel of staphylococcal alpha-toxin

Staphylococcus aureus alpha-toxin is a hydrophilic polypeptide of 293 amino acids that produces heptameric transmembrane pores. During assembly, the formation of a pre-pore precedes membrane permeabilization; the latter is linked to a conformational change in the oligomer. Here, 41 single-cysteine replacement toxin mutants were thiol-specifically labelled with the polarity-sensitive fluorescent probe acrylodan. After oligomerization on membranes, only the mutants with acrylodan attached to residues in the sequence 118-140 exhibited a marked blue shift in the fluorescence emission maximum, indicative of movement of the fluorophore to a hydrophobic environment. Within this region, two functionally distinct parts could be identified. For mutants at positions 126-140, the shifts were partially reversed after membrane solubilization by detergents, indicating a direct interaction of the label with the membrane lipids. Membrane insertion of this sequence occurred together with the final pre-pore to pore transition of the heptamer. Thus residues 126-140 constitute a transmembrane sequence in the pore. With labelled residues 118-124, pre-pore assembly was the critical event to induce the spectral shifts, which persisted after the removal of membrane lipids and hence probably reflects protomer-protomer contacts within the heptamer. Finally, a derivative of the mutant N121C yielded occluded pores which could be opened by reductive reversal of the modification. Therefore this residue probably lines the lumen of the pore.

Aberration-free stretcher design for ultrashort-pulse amplification

A novel aberration-free pulse stretcher design is presented. This system permits the stretching of a 30-fs pulse to 300 ps and recompression to a duration of 33 fs, limited by the spectral clipping.

Staphylococcal alpha-toxin, streptolysin-O, and Escherichia coli hemolysin: prototypes of pore-forming bacterial cytolysins

Staphylococcal alpha-toxin, streptolysin-O, and Escherichia coli hemolysin are well-studied prototypes of pore-forming bacterial cytotoxins. Each is produced as a water-soluble single-chain polypeptide that inserts into target membranes to form aqueous transmembrane pores. This review will compare properties of the three toxin prototypes, highlighting the similarities and also the differences in their structure, mode of binding, mechanism of pore formation, and the responses they elicit in target cells. Pore-forming toxins represent the most potent and versatile weapons with which invading microbes damage the host macroorganism.

Assessment of urinary gonadotropin in solid carcinomas other than gynecological tumors

To the already long list of existing tumor markers, a new marker has been recently added, the urinary gonadotropin peptide (UGP). This marker is determined in the urine of cancer patients and is considered to be particularly specific for ovarian carcinomas. The purpose of our study was to assess the specificity of UGP in a variety of malignancies other than ovarian carcinomas, e.g., breast, colonic, lung, and urogenital tumors (n = 50 each). The tumors were compared with benign lesions of the same organs. Urine samples of 50 healthy donors served as controls. The 450 urine samples were tested in duplicate using the UGP EIA-kit from Ciba Corning Diagnostics. All tumors were staged and histologically classified. For normalization in all samples, creatinine levels were determined. UGP was found in all tested tumors, however, with very low sensitivity of 20% in urogenital tumors, 46% in lung, and 30% or 27% in colon and breast carcinomas, respectively. The specificity of UGP was comprised between 100% (breast) and 88%. Clearly elevated UGP-concentrations were seen in postmenopausal women. A comparison of UGP with the optimal markers for each tumor system showed that UGP is not superior to these markers. However, we can confirm UGP as being an optimal marker for gynecological carcinomas.

Early first-trimester ultrasound provides a window through which the chorionicity of twins can be diagnosed in an in vitro fertilization (IVF) population

PURPOSE

Early and accurate diagnosis of placentation alerts the obstetrician to potential clinical sequelae. The reproductive endocrinologist has a unique opportunity to sonographically evaluate the very early intrauterine pregnancy. We undertook this study to determine whether chorionicity could accurately be predicted using early first-trimester transvaginal ultrasound.

RESULTS

Of 47 sets of twins conceived through our IVF-ET program, all underwent detailed transvaginal sonography. These findings were then compared with results of placental pathology examination, after birth. Transvaginal sonography was performed 41 days following embryo transfer. All 3 monochorionic placentas were correctly predicted by ultrasound, while the remaining 44 placentas were dichorionic.

CONCLUSIONS

The significance of our findings lies both in our 100% accuracy in diagnosis and in the extremely early gestational age at which we were able to establish correctly the diagnosis of chorionicity. The errors in diagnosis made by previous investigators were often the result of not recognizing single placentae which were later histologically shown to be the result of placental fusion. The infertility specialist has a unique window of opportunity to evaluate placentation and should provide useful information regarding chorionicity to the obstetrical team.

Differences in cancer incidence, mortality, and survival between African Americans and whites

This report highlights selected evidence of different cancer patterns among African Americans and whites and considers potential risk factors associated with these cancers. During the years 1987 to 1991, African Americans experienced higher incidence and mortality rates than whites for multiple myeloma and for cancers of the oropharynx, colorectum, lung and bronchus, cervix, and prostate. African Americans had lower incidence and mortality for cancer of the urinary bladder. The incidence of breast cancer was higher among white women, but mortality was higher among African American women. Five-year relative survival for the period 1983 to 1990 was generally lower among African Americans than whites for cancers of the oropharynx, colorectum, cervix, prostate, and female breast but slightly higher for multiple myeloma. From 1973 to 1991, there were significant declines in cervical cancer incidence among women of both races, oropharyngeal cancer mortality among whites, and bladder cancer mortality for whites and African Americans. Risk factors for the more prominent cancers suggest that efforts aimed at changing lifestyles, achieving socioeconomic parity, and insuring environmental equity are likely to relieve African Americans of much of their disproportionate cancer burden.

Key residues for membrane binding, oligomerization, and pore forming activity of staphylococcal alpha-hemolysin identified by cysteine scanning mutagenesis and targeted chemical modification

The alpha-hemolysin (alpha HL) polypeptide is secreted by Staphylococcus aureus as a water-soluble monomer that assembles into lipid bilayers to form cylindrical heptameric pores 1-2 nm in effective internal diameter. We have individually replaced each charged residue (79 of 293 amino acids) and four neutral residues in alpha HL with cysteine, which is not found in the wild-type protein. The properties of these mutants have been examined before and after modification with the 450-Da dianionic sulfhydryl reagent 4-acetamido-4'-((iodoacetyl)amino)stilbene-2,2'-disulfonate (IASD). This modification was highly informative as 28 of 83 modified polypeptides showed substantially reduced pore forming activity on rabbit erythrocytes (rRBC), while only five of the unmodified cysteine mutants were markedly affected. Through detailed examination of the phenotypes of the mutant and modified hemolysins, we have pinpointed residues and regions in the alpha HL polypeptide chain that are important for binding to rRBC, oligomer formation and pore activity. Residues in both the N-terminal (Arg-66 and Glu-70) and C-terminal (Arg-200, Asp-254, Asp-255, and Asp-276) thirds of the protein are implicated in binding to cells. The His-35 replacement mutant modified with IASD was the only polypeptide in this study that failed to form SDS-resistant oligomers on rRBC. Altered hemolysins that formed oligomers but failed to lyse rRBC represented the most common defect. These alterations were clustered in the central glycine-rich loop, which has previously been implicated as a component of the lumen of the membrane-spanning channel, and in the regions flanking the loop. Alterations in mutant and modified hemolysins with the same defect were also scattered between the N terminus and His-48, in keeping with previous suggestions that an N-terminal segment and the central loop cooperate in the final step of pore assembly.

Substance P (NK1)- and neurokinin A (NK2)-receptor gene expression in inflammatory airway diseases

The tachykinin neuropeptides substance P and neurokinin (NK) A have been postulated to participate in the inflammatory reaction in airways of smokers and asthmatics. We have examined the hypothesis that the expression of one or more of the three cloned tachykinin receptors (NK1, NK2, and NK3) is increased in inflammatory airway disorders, which could result in augmentation of the effect of released tachykinin neuropeptides. NK1 receptor and NK2 receptor but not NK3-receptor mRNA were detected by ribonuclease protection assay in RNA from both cartilaginous and membranous bronchi and subpleural lung. In lung samples containing membranous airways, NK2-receptor mRNA expression was increased fourfold in asthmatics compared with nonsmoking controls, whereas NK1-receptor mRNA levels were similar in the two groups. NK1- and NK2-receptor mRNA expression was increased twofold in smokers without airflow obstruction compared with nonsmokers, whereas NK1-receptor mRNA expression was significantly lower in patients with chronic obstructive pulmonary disease compared with smoking controls. In situ hybridization indicated NK1-receptor mRNA was expressed in submucosal glands and airway epithelial cells, whereas NK2-receptor and NK3-receptor mRNA were not detected. These observations have implications for the pathophysiology and treatment of both asthma and tobacco smoke-induced airway inflammation.

Murine epidermal growth factor (EGF) fragment (33-42) inhibits both EGF- and laminin-dependent endothelial cell motility and angiogenesis

Laminin, murine epidermal growth factor (mEGF), and the synthetic laminin peptide Lam.B1(925-933) (a linear peptide from the B1 chain of murine laminin, CDPGY1GSR-amide) all stimulate endothelial cell motility above basal rates, whereas a synthetic mEGF fragment, mEGF33-42 (a linear peptide from the C-loop of mEGF, acetyl-C-[S-Acm]-VIGYSGDR-C-[S-Acm]-amide), inhibits motility. In both human SK HEP-1 and embryonic chick endothelial cells, mEGF33-42 blocks both EGF- and laminin-stimulated locomotion of endothelial cells. In vivo, mEGF33-42 also blocks both laminin- and mEGF-induced angiogenesis in the chick. In the human cell line. Lam.B1(925-933) has an additive effect in coincubation with either laminin or mEGF, but it blocks their effects in the chick cells. Lam.B1(925-933) alone stimulates angiogenesis in the chick but blocks laminin-induced angiogenesis. Thus, mEGF33-42 acts as a general laminin antagonist, whereas Lam.B1(925-933) acts as a laminin agonist in human cells, but in chick cells it acts as a partial antagonist. We propose that the presence of an anionic group at the eighth residue of mEGF33-42 may be the source of the antagonistic effects seen with this peptide as compared with the laminin fragment. These findings have important implications in the design of human antiangiogenic agents, and also in the use of chick models in the study of human disease.

Cytokine profile of circulating T cells of leprosy patients reflects both indiscriminate and polarized T-helper subsets: T-helper phenotype is stable and uninfluenced by related antigens of Mycobacterium leprae

Cytokine profiles of circulating mononuclear cells were studied with the aim of delineating T-cell subsets in leprosy patients with active disease. Using reverse transcriptase-polymerase chain reaction (RT-PCR) for cytokine mRNA and enzyme-linked immunoassay (ELISA) for the secreted products, interferon-gamma (IFN-gamma), interleukin-4 (IL-4), IL-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF) were studied. Three antigens, native Mycobacterium leprae, a recombinant antigen LSR/A15 of M. leprae and peptide 624 spanning 58-77 amino acids of the latter, were used to induce cytokine expression and release. Half of the subjects, irrespective of the clinical type or antigen used, showed a mixed T-helper type 0 (Th0)-like cytokine pattern, with evidence of the concomitant presence of IFN-gamma and IL-4. The remainder showed a polarized pattern based on the type of leprosy. Lepromatous patients with disseminated disease had Th2-type cytokines, with IL-4 but not IFN-gamma. In contrast, tuberculoid leprosy patients with localized disease showed a Th1-like profile, with the presence of IFN-gamma but not IL-4. Of interest was the stability of the Th phenotype for M. leprae-related antigens. Both the recombinant and the peptide antigens induced the same phenotype as the natural M. leprae bacillus in all except four of 45 leprosy patients.